What is the difference between Arupaloka and Nibbana? Arupaloka is a state before reaching Nibbana.

Can i say that the difference are no incarnation, no dukkha and has Buddhism teaching in Nibbana?

Why is Arupaloka does not has Buddhism to study?

> The first level, the Realm of Formlessness (Arupaloka), consists of
> four planes of brahmas who have no physical body, consisting entirely
> of mind, but who may create a physical body if they want to be seen.
> They are not completely free from the fetters of suffering (dukkha),
> but the dukkha experienced here is much less intense than that
> suffered in the Rupaloka. These brahmas are unable to hear the
> teachings of the Buddha (dhamma) and they can never become
> enlightened.
[Buddhist rebirth in different planes of existence][1] 


  [1]: https://blogs.bl.uk/asian-and-african/2016/03/buddhist-rebirth-in-different-planes-of-existence.html